It's not the damping oil. That's just the Prep-M lubricating grease. It might have been overpacked at the factory or at the shop and/or the seals may not be up to snuff. If it was damping oil from a blown bottom seal you would have hydraulic lockout (i.e. limited travel). My buddy has the same fork on his Giant Rainier and it did the same thing. His works just fine though. So if it seems to be working okay, it's probably fine. You should be able to wipe it off and keep going.